Beam compass



June 20, 1950 w. K. LANKFORD BEAM COMPASS Filed March '7, 1947 ATTOIQIVEYJ Patented June 20, 1950 UNIT ED STAT ES PATENT F F ICE BEAM COMPASS William K,..Lankford, Roanoke, Va.

Application March 7, 1947; Serial No. 7333219 LGlaim. l

'My invention relates to compasses, particularly: toa beam compass of new and novel designiwhi'ch may be used? easily by draftsmen and others'for theaccurate drawing of circles andarcsrhaving radii of greater length than the range-of an ordinary compass.

It is a principal object; of my invention to-proride a beam compass which will have both hori' zontal' andvertical balanced-n used'ueto a novelbracing-- and ball-bearing arrangement ofv the stem' point, imparting a floating motion-to the-marking point; for ease in using.

It is an important object of my invention to provide a beam compass of the character desenibed having extensiblemembersreasily assembled for lengthening the beam;

It is a still further object. of,.my, invention to provide a beam compass of the character described which is extremely accurate, and which, once set,- w-iil-n0t easily get-out er adjustment,

It is a still further objector. my invention. to

provides-beam compasswh ich is. simple tomanufacture, easy: to-assemble; andhwhich camber. com.- pac-tly'arranged for safe. keeping. in a relatively smallrcarrying case,

other objects. and advantages: ofimy invention will becomeapparent. during the. course. oi?" the following specification, and accompanying drawings, forming part of the specification, in which like numerals are used to designate like parts throughout the specification and drawings.

In the drawings:

Figure 1 is an elevational view of a beam compass embodying my invention.

Figure 2 is a plan view of the same.

Figure 3 is a longitudinal section, partly in elevation, of the bearing and stem point.

Figure 4 is a longitudinal section through the marking point and slidable mounting structure, the securing nut being shown on the marking point, and

Figure 5 is an end elevatio-nal view of the marking point.

Referring now in detail to the drawings, the numeral 6 refers generally to a bearing member formed as a ring having an outwardly extending arm 8 with an apertured recess 9 at the end thereof. Anti-friction ball-bearings I!) having two concentric races are arranged in the ring 8 for a purpose which will hereinafter become apparent. A cylindrical stem member ll, tapered to a point l2 at one end and having external threads l3 at its opposite end and an annular flange l4 intermediate the said ends, is arranged to pass through said bearing and depend therefrom the topoi the flange M bearing against the" lower surface of the hearing when the said stem point is secured thereto A- bracing member in the form ofa, cylindrical main stem or. handle: l5

ha-vingiian enlarged. diametered knurled portion IE;- is provided with: an internally threaded aperture H in which the upper threaded portion tezof-thesternjmemben H is threadedly engaged seaures the said stem: member: I l in the bearing member-6 andsisxusedito hold the said point: 12-

on: the work. when the: compass is being used; therebeing'a knnrledziporticn I18 on the upper end of. stem tor facility inholding it.. zit-calibrated; extension member I9; whiclrmay' be either square. or rectangular incross section, is reduced adjacent one end thereof to provide a tangue'zliradaptedto engageiwithin the recess er lie-ha aeeuredttherein by aset screw 21 thread-- ire an internally"- threaded opening: 22 inthezame mthezstenr of'ithesaidsetscrew 2| upon: the: rennced; portion, of" the said incmbeirlls thaiiinction between the said: exten-= sinn member; I19 therarmilbeingapredeter minem distance: from the? stem pointw Thanumeral; 2;:3 designatesrthe; marking point assembly of the invention: I t compri'sesa longitud nal holloimmember: 24ihalvi'nganinterna1 bore 25 extending therethrough, the said bore being slightly greater in its cross-sectional dimensions than the member I9 to permit a sliding motion of the said assembly 23 when translated on the member l9, and a dependent tapered and split clutch portion 26 intermediate the ends of the longitudinal member 24, the jaws 21 of said clutch being spaced apart to engage a pencil lead 28, or a similar scribing point as desired, therebetween. The clutch 26 is also provided with exterior screw threads 29 above the taper and adjacent the bottom of the member 24 adapted to threadedly engage, as at 30, the internal threads of a nut 3| having an internally tapered portion of its bore 32 adapted to have a sliding fit on the tapered portion of the clutch 26, to be drawn upward thereon by the tightening of the nut thereby forcing the jaws 21 toward each other to secure the lead as therebetween. The member 24 is also provided with an internally threaded opening 33' axially aligned with the portion 26 adapted to threadedly engage a set screw 34 for securing the assembly on the member I9 in a predetermined position relative to the stem point l2, to describe a circle within the range of the calibrated mem- Igor l9, or a similar but longer calibrated mem- The operation of a beam compass is too well known to need detailed explanation. It is sumcient to state, that by holding the compass at the main stem 15, the point I2 upon a center and the lead 28 spaced a determinable distance away and resting on a paper or other surface in the same plane as the point l2, the user may swing the marking point through a complete circle or an arc of any length less than a circle as desired within the limits of the calibrated member I9, only one hand being needed to securely hold the main stem. The ball-bearings Ill permit full floating movement of the marking point and, in association with the horizontal and vertical balance of the compass, accuracy and ease of performance is assured.

It frequently becomes necessary to draw a circle having a radius beyond the range of the extension I9. I have provided for such a contingency by means of a stabilizing element 35 and a lengthening bar 36, of similar cross-section to the extension member l9. The element 35 is arranged with a through bore 31 large enough to permit snug engagement of the member 19 and bar 36 therein, there being spaced apart threaded openings 38 in the top of said element to threadedly engage a pair of set screws 39 adapted to impinge upon the respective adjacent opposed ends of the said member I9 and bar 36 when inserted in opposite ends of the said element to secure them firmly therein. The marking point assembly will then be placed on the said bar for relative translative movement in the same manner as heretofore described. This will greatly increase the working range of the compass, and it may be used in exactly the same manner already described in connection with extension 19.

I prefer to make all of the parts of my beam compass of aluminum or 1020 steel, except the ball-bearings ill which will be of the standard type supplied by ball-bearing manufacturers.

.I have thus described my invention in the form best known to me at this time. It is to be understood however, that changes in the shape and arrangement of the parts may be made within the scope of the sub-joined claim without departing from the spirit of the invention.

Having thus described my invention, 1 claim:

In a beam compass, a beam adapted to swing horizontally about a fixed center, a generally flat and relatively thin bearing plate having a large transverse bore extending therethrough, said bearing plate including an integral substantially radial extension having a longitudinal opening forming a socket receiving one end of said beam for securing the bearing plate thereto, a single ball bearing mounted within said bore of the bearing plate and including a freely rotatable inner race having a bore, the inner race being of substantially the same axial thickness as the bearing plate, an elongated stem mounted within the bore of the inner race and having an annular radial flange contacting one end of the inner race to prevent axial movement of the stem in one direction, a pointed centering extension formed integral with the stem and projecting axially beyond said annular flange, the stem having a screw threaded extension extending axially beyond the opposite end of the inner race, and an elongated rod serving as a handle extending axially beyond said screw threaded extension and provided in its inner end with a screw threaded opening receiving the screw threaded extension therein, the inner end of said rod engaging the adjacent end of the inner race and clamping the inner race between said annular flange and rod, whereby said beam may rotate freely about said pointed extension while the pointed extension, inner race and rod serving as a handle remain stationary.

WILLIAM K. LANKFORD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

